By this time, growers should have met with their PCAs to create a detailed game plan for bloom that clearly states how potential disease and pest problems will be addressed.
Looking toward management during bloom, growers and PCAs must work together to determine if bloom is an effective time to treat for existing issues, with the ultimate goal of deciding what issues are absolutely appropriate and necessary to treat during bloom.
The Almond Board sat down with David Haviland of the University of California and Emily Symmes of Suterra to create a list of four questions growers should ask their PCAs leading up to and during boom.
1. What is the weather telling us?
The risk of bloom-time diseases varies greatly throughout California and depends heavily on the amount of rainfall received, as well as temperature and other environmental factors. In the southern San Joaquin Valley, due to lower levels of rainfall, there is a relatively low risk of disease. This means growers typically only have to choose between applying none or one fungicide spray during bloom. Conversely, orchards north of Sacramento are typically much more susceptible to bloom diseases because of greater levels of rainfall, meaning growers have more decisions to make to determine if and when applications are necessary.
2. Am I seeing peach twig borer (PTB) in my orchard?
Sightings of PTB are much rarer in the San Joaquin Valley than in the Sacramento Valley. Still, it’s important that all growers understand how to address the pest.
According to experts at the University of California Cooperative Extension (UCCE) and UC Statewide IPM Program (UCIPM), the only pest that should be considered for treatment during bloom is PTB. There are three windows of opportunity for growers to treat this pest: dormancy, bloom and spring. In order to prevent impacts on water quality and run-off, though, growers should avoid applications during dormancy as much as possible. This leaves bloom and spring as more desirable times to treat.
However, growers must consider honey bee activity in their orchards and do everything in their power to protect bee health. This means that if an application to combat PTB is absolutely necessary during bloom, only products containing Bacillus thuringiensis (Bt) as an active ingredient should be used to prevent harm to honey bees. For more information on PTB symptoms and treatment, visit the UC IPM website.
3. If I absolutely must apply a pesticide during bloom, what guidelines should I follow?
Pesticides are inherently hazardous to varying degrees. In order to help PCAs and growers make responsible, informed choices on proper applications, the UCIPM Program created the “Bee Precaution Pesticide Ratings” guide. The guide is founded on the most up-to-date research studies of known pesticide impacts on adults and honey bee brood. It’s important to note, however, that the ratings for each compound are only for the active ingredient or common name of that compound, and do not include any impact associated with adjuvants or with making tank mixes including multiple compounds.
Once growers and PCAs have agreed upon an application, it’s imperative that before any spray takes place the grower/PCA visits BeeWhereCalifornia.com or contacts the local county agricultural commissioner to locate hives within a 1-mile radius of the determined spray site. Growers should also notify the appropriate beekeeper/s of the upcoming spray.
From there, the application should only be made in the late afternoon, or evening, when bees and pollen are not present in the orchard. In addition, Symmes said that growers must make sure that the residue has completely dried before the bees return to pollinating the next day.
For more information on proper application, visit page 10 of the Almond Board of California’s Honey Bee Best Management Practices.
4. If a fungicide application is needed, what is absolutely required in the tank to protect my crop?
If your PCA recommends a fungicide application, be mindful that adjuvants – unless specified otherwise on the label – should not be combined with fungicides during bloom. Some fungicides are already formulated with adjuvants and, with few exceptions, added adjuvants do not statistically improve the efficacy of fungicides for managing disease. Furthermore, because there’s no shortage of potential tank mixes among growers, UCCE fungicide efficacy information does not take into account the addition of adjuvants to any studied fungicides, as the UCCE simply cannot recreate every possible mix nor can they know how every possible application will impact honey bees.
When in doubt, always err on the side of bee safety. For growers in the southern San Joaquin Valley, especially, it’s important to realize that, more often than not, no application is necessary during bloom.
“If you’re a PCA in the southern San Joaquin Valley, you know there’s no need to spray insecticides during bloom. The only viable question is, “Do we need to make a fungicide application?” said Haviland.
For growers throughout the state, it all comes down to maintaining a delicate balance between protecting your crop from disease and pest pressures while simultaneously protecting honey bee health.
